<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .father {
        background-color: pink;
        height: 200px;
        width: 500px;
        margin: 0 auto;
      }
      .son1 {
        background-color: green;
        height: 40px;
        margin: 0 -20px;
      }
      .son2 {
        background-color: cyan;
        width: 300px;
        height: 40px;
        margin: 0 -20px;
      }
    </style>
  </head>
  <body>
    <h3 style="text-align: center;">什么是充分利用可用空间??</h3>
    <div class="father">
      <div class="son1"></div>
      <div class="son2"></div>
    </div>
  </body>
</html>
